Last month, the Obama administration released a plan designed to end homelessness in 10 years. The goal reflects new optimism among academics and advocates that homelessness is not an intractable feature of urban life, as it has sometimes seemed, but a problem that can be solved. This belief is fueled by recent research debunking a number of long-standing myths about homelessness in America -- and showing that many of our old policies were unwittingly making the problem worse.

1. Homelessness is usually a long-term condition.

To the contrary, the most common length of time that someone is homeless is one or two days, and half the people who enter the homeless shelter system will leave within 30 days, never to return.

Long-term homelessness is relatively rare. According to the Department of Housing and Urban Development, about 2 million people in the United States were homeless at some point in 2009 (meaning they stayed overnight in a shelter or in a place not meant for human habitation). But on any given day, only about 112,000 people fit the federal definition of "chronic homelessness," which applies to those who have been continuously homeless for a year or more, or are experiencing at least their fourth episode of homelessness in three years.

Nearly all of the long-term homeless have tenuous family ties and some kind of disability, whether it is a drug or alcohol addiction, a mental illness, or a physical handicap. While they make up a small share of the homeless population, they are disproportionately costly to society: They consume nearly 60 percent of the resources spent on emergency and transitional shelter for adults, and they occupy hospitals and jails at high rates.

2. Most of the homeless have a severe mental illness.

Because the relatively small number of people living on the streets who suffer from paranoia, delusions and other mental disorders are very visible, they have come to stand for the entire homeless population -- despite the fact that they are in the minority. As a result, many people falsely concluded that an increase in homelessness in the 1980s resulted from the deinstitutionalization of psychiatric care in the 1960s and 1970s.

In my own research, I have calculated that the rate of severe mental illness among the homeless (including families and children) is 13 to 15 percent. Among the much smaller group of single adults who are chronically homeless, however, the rate reaches 30 to 40 percent. For this population, mental illness is clearly a barrier to exiting homelessness.

But depending on a community's resources, having a severe mental illness may, paradoxically, protect against homelessness. Poor people with severe psychiatric disabilities may have more means of support than other people in poverty because they are eligible for a modest federal disability income, Medicaid, and housing and support services designed specifically for them. Not so for the other childless singles -- including ex-convicts, people with drug addictions and the able-bodied unemployed -- who make up the majority of the nation's homeless population.

3. Homeless people don't work.

According to a 2002 national study by the Urban Institute, about 45 percent of homeless adults had worked in the past 30 days -- only 14 percentage points lower than the employment rate for the general population last month. The number of working homeless would probably be even higher if "off the books" work was included. Whether scavenging for scrap metal or staffing shelters, many homeless people adopt ingenious ways to subsist.

A recent job loss is the second most common reason people say they became homeless. In a study my colleagues and I are completing, we observe a steep drop in earned income in the year prior to the onset of homelessness. Interestingly, those people who return to work show a steep recovery in earned income three years after their initial homeless spell. Our preliminary data also suggest that about a third of the chronically homeless eventually end up working, thanks, quite likely, to substance-abuse recovery.

4. Shelters are a humane solution to homelessness.

When homelessness became a national epidemic in the 1980s, reformers responded with emergency shelters that were meant to be temporary havens. But as homelessness became more entrenched, so did shelters: Their capacity more than doubled by the late 1980s, then again a few years later, and then again by 2000. Along the way, they became institutionalized way stations for lots of poor people with temporary housing crises, including those avoiding family conflicts, leaving prison or transitioning from substance-abuse treatment.

Large shelters are notoriously overcrowded and often unruly places where people experience the ritualized indignities of destitution: long lines for bedding or a squeeze of toothpaste; public showers; thieves; conflict. Many people have voted with their feet, and as a result, street homelessness persists.

Shelters may be the final safety net, but that net scrapes perilously close to the ground. To be in a shelter is to be homeless, and the more shelters we build, the more resources we divert from the only real solution to homelessness: permanent housing.

5. These poor you will always have with you.

Researchers and policymakers are newly optimistic about the prospect of ending homelessness. For two decades, the goal of our homeless programs was to first treat people for their myriad afflictions (substance abuse, say, or illness) and hope that this would lead them out of homelessness. Now, the attention has shifted to the endgame: Get people back into housing as quickly as possible, the new thinking goes, and the treatment for everything else can quickly follow -- and with greater benefits.

People who haven't had a private residence in years have succeeded in these new "housing first" programs, which place the homeless directly into their own housing units, bypassing shelters. Rent is subsidized and services are provided to help these tenants maintain their housing and be good neighbors.

According to HUD, the government has funded more than 70,000 such housing units since 2001. Meanwhile, the number of chronically homeless nationwide has decreased by a third since 2005, to 112,000.

The Obama administration's new Homelessness Prevention and Rapid Re-Housing program takes a similar approach, giving people suffering temporary housing crises modest cash and service support, allowing them to avoid shelters or get out of them more quickly.

The cost of these programs is partly offset by reductions in expensive hospitalizations, arrests and shelter stays by the chronically homeless -- to say nothing of the moral victory a society can claim in caring for its most vulnerable.